This invention relates to valve apparatus for regulating flow of heat exchange liquid such as coolant, depending on the temperature of a second liquid, such as transmission oil.
A variety of systems are known for regulating the temperature of a liquid, such as oil, using a heat exchanger or an oil cooler. In particular, it is known that one can regulate the temperature of oil used in a transmission with the objective of maintaining the temperature of the oil within a desirable temperature range so the temperature of the oil is neither too hot nor too cold. In one particular system for regulating the temperature of transmission oil by means of an oil cooler, a mixing valve is provided which is able to direct either hot coolant from a vehicle engine, for example, or cold coolant flowing from a radiator, for example, through the heat exchanger so that the heat exchanger works as a heater or as a cooler. A known form of mixing valve for regulating the temperature of a liquid such as coolant includes a valve housing having first and second chambers formed therein as well as inlet and outlet ports for the flow of a liquid into and out of the first chamber. Further ports are provided in the housing for the flow of coolant at either an elevated temperature or at a lower temperature into and out of the second chamber. A linear actuator in the form of a wax motor is mounted in the first chamber and has an actuator body which contains the wax and a piston movable to an extended position by expansion of the wax when the temperature of the wax is increased to a predetermined level. Since a substantial portion of the actuator body is located in the first chamber, the temperature of the actuator body and its wax is determined to some extent at least by the temperature of the liquid flowing through the first chamber. A valve mechanism including a valve spool is operable by the linear actuator with one end of the spool being operably connected to the piston for movement therewith. The valve mechanism is located in the second chamber of the housing and is capable of controlling the flow of both coolant at the elevated temperature and coolant at the lower temperature through the second chamber.
One difficulty with this known mixing valve is that it is possible for the temperature of the wax in the wax motor actuator to be influenced by not only the temperature of the liquid flowing through the first chamber but also the temperature of the coolant in the second chamber since one end of the wax motor actuator and its piston is either adjacent to or in the second chamber. The influence of the temperature of the coolant can at least in some cases adversely affect the proper operation of the wax motor actuator.
Another difficulty with the aforementioned known mixing valve is that it requires a number of separate components or parts mounted within the valve housing for the purpose of mounting the linear actuator. In particular, in this known construction, a separate, cylindrical retainer cap is mounted in the housing between the first and second chambers and is held in place by means of a retainer clip. An end section of the wax motor actuator is mounted in this retainer cap. The annular joint between the retainer cap and the housing is sealed by an O-ring extending around the cap and an additional O-ring is required to seal the joint between the cap and the actuator.
A further difficulty with the aforementioned known mixing valve is that the valve housing employs a separate end fitting which forms one end of the second chamber and which is held in the main body of the valve housing by means of a retainer clip. This end fitting, which forms one inlet for coolant to flow into the second chamber, has mounted therein a separate valve spool supporting member which is mounted within the inlet passage by means of a retainer clip.